Automatic warehousing systems of this type have been known, a typical one of which is disclosed in, for example, Japanese Utility Model Laid Open Publication No. 1-169511.
In this prior art disclosure, the automatic warehousing system includes a rack having a plurality of load storing spaces, a load sorting device disposed outside of one end of each rack, a load handling mobile crane movable on a travel passage extending along the front side of the rack and load sorting device, and an safety fence erected laterally along one side of the load sorting device and in opposed relation to the travel passage, the safety fence being provided with a crane control panel and an access door.
According to this known arrangement, it is possible to carry out delivery of load between any particular load storing space and the load sorting device by operating the load handling mobile crane through control from the crane control panel. For maintenance and checking of the rack and mobile crane, an operator opens the access door for entry in the travel passage while the mobile crane is held in its non-operating state.
Inputting of instructions to the crane control panel is carried out in such a way that a mode switch for switching from a load entry mode to a load exit mode and vice versa and a finish switch manipulatable at the end of an operation are manipulated to give instructions as to the mode of required operation, i.e., load entry or load exit, and as to operation ending, and in addition a particular number for the load storing space into or from which a load is to be placed or withdrawn is input by using a rack number card in which the rack number is printed in bar code, such card being provided for each respective load storing space. Rack number cards are kept in orderly arrangement in a card holding case disposed adjacent the warehousing installation.
In carrying out load entry and delivery operations, the operator determines the desired rack number from the name of goods written in a load entry/delivery slip and according to an item-rack number list, takes out a rack number card corresponding to the rack number from the card holding case through card search, causes the rack number card to be read by a bar code reader, and then inputs the rack number to the crane control panel. After the load entry/delivery operation is executed, the rack number card is put back into position in the card holding case. Inventory management is carried out by hand writing the name of goods and quantity received or delivered in a control sheet attached to the rack number card.
However, such prior art practice involves a problem that a wrong rack-number card may sometimes be fetched, instead of the desired rack-number card, out of a series of rack number cards arranged in the card holding case. Another problem is that the rack number card taken out may be improperly placed back into the card holding case or may be left unreturned to the card holding case. All these problems are likely to occur from or in connection with the use of rack-number cards.
Further, the prior art system requires some operations to be carried out by the operator. That is, the operator must check to see that the name of goods for each load is correct in relation to the corresponding rack number and must also maintain control sheets in order. This naturally results in poor operating efficiency and is likely to induce operational errors.